Ventilator for an anesthesia gas machine

ABSTRACT

Located adjacent an anesthesia gas machine is a pair of opposed, concave paddles, relatively movable toward and away from each other, alternately squeezing and releasing a conventional, flexible, breathing bag interposed between the paddles. The frequency of the paddle opening and closing cycle can be controlled; and a warning mechanism monitors and indicates excessive back pressure during bag compression, thereby alerting the anesthetist to a change in the patient&#39;&#39;s responses.

United States Patent 11 1 Bauman 1451 Sept. 11, 1973 1 VENTILATOR FOR AN ANESTHESIA GAS MACHINE [76] Inventor: Jack Bauman, P.O. Box 25310, Los

Angeles, Calif. 90025 [22] Filed: June 1, 1971 [21] Appl. No.: 148,580

52 us. c1. 128/145.6

51 1111. c1 A6lm 16/00 581 Field of Search 128/188, 145.8, 145.5, 128/1456, 145.7, 202

[56] References Cited UNITED STATES PATENTS 2,582,210 1/1952 Stanton 128/188 3,566,387 2/1971 Schoener... 128/1455 1,202,125 10/1916 Tullar 128/1457 2,591,120 4/1952 Blease.... 128/1456 3,114,365 12/1963 Franz 128/1458 3,527,555 9/1970 Schreiber 128/1458 FOREIGN PATENTS OR APPLICATIONS 1,084 0/1909 Great Britain 128/202 Primary ExaminerRichard A. Gaudet Assistant ExaminerG. F. Dunne Attorney-Lothrop & West 5 7 1 ABSTRACT Located adjacent an anesthesia gas machine is a pair of opposed, concave paddles, relatively movable toward and away from each other, alternately squeezing and releasing a conventional, flexible, breathing bag interposed between the paddles. The frequency of the paddle opening and closing cycle can be controlled; and a warning mechanism monitors and indicates excessive back pressure during bag compression, thereby alerting the anesthetist to a change in the patients responses.

6 Claims, 4 Drawing Figures PAIENIEnsEM a ma 757, 776

sum 1 or 5 INVENTOR.

JA CK BAUMfl/V PAIENTEUSEH 1191s 757.

sum 2 OF 3 INVENTOR. JAC K BAU MAN ATTOQNE Y5 VENTILATOR FOR AN ANES'IIIESIA GAS MACHINE The invention relates to improvements in accessories for anesthesia apparatus and, more particularly, to improvements in the operation of the flexible gas reservoir, or breathing bag, customarily used as a part of the lung ventilating system.

Heretofore, the anesthetist has alternately applied manual pressure to the bag and released the bag, to help the patient breathe during the administration of anesthesia. The bag is squeezed during inhalation and released during exhalation.

Manipulation of the bag by the application of hand pressure affords a valuable indication as to whether proper lung ventilation is taking place, according to the feel provided by the bag. That is to say, the bag pressure along with other indicators reveals to an experienced anesthetist whether lung ventilation is proceeding in a satisfactory manner. However, it is often difficult to time the rate of respiration soas to provide the optimum pattern, wherein each cycle of respiration, timewise, consists of approximately one-third inhalation time and two-thirds exhalation time plus a short pause after each. So also, the extent of the pressure manually exerted is subject to fluctuation, depending upon fatigue, degree of concentration and similar subjective factors.

It is therefore an object of the invention to provide a ventilator for an anesthesia gas machine which can be regulated so as to operate at a predetermined optimum pattern of respiration, at a predetermined pressure and at a predetermined optimum respiration rate, or respiratory frequency.

It is another object of the invention to provide a ventilator which affords a warning when a predetermined back pressure threshold is exceeded, thereby alerting the anesthetist that operation of the machine or ventilation of the patient has departed from the norm, such as might be occasioned, for example, from a bronchial spasm, an obstruction in the ventilation flow path or decreased compliance of the patient.

It is yet another object of the invention to provide a ventilator in which aseptic techniques can more readily be applied owing to the ease with which the bag can be removed, cleaned and replaced.

It is a further object of the invention to provide a ventilator which is relatively economical, both with respect to original acquisition as well as upkeep costs, yet which is reliable, sturdy and long-lived.

It is still a further object of the invention to provide a ventilator which functions in a manner such that its operation can readily be learned.

It is yet a further object of the invention to provide a ventilator which is readily accessible and which enables the anesthetist to resume manual operation at any time or to place the bag in the device substantially instantaneously and without pause in the respiration cychine providing, as a part of the lung ventilation sys tem, a flexible, gas reservoir breathing bag;

FIG. 2 is a fragmentary perspective view, to an enlarged scale, of the housing and paddle structure, portions of the housing being broken away to reveal details of the paddle drive mechanism;

FIG. 3 is a fragmentary sectional view to an enlarged scale, of the warning signal switch mechanism, the section being taken on the line 3-3 in FIG. 2; and,

FIG. 4 is a diagram of the electrical system.

While the ventilator of the invention is susceptible of numerous physical embodiments, depending upon the environment and requirements of use, substantial numbers of the herein shown and described embodiment have been made, tested and used, and all have performed in an eminently satisfactory manner.

The ventilator of the invention, generally designated by the reference numeral 12, is customarily located adjacent a conventional anesthesia gas machine 13 in an operating room. The machine 13 is provided with the usual compressed gas bottles 14, conduits 15, pressure relief valve 20, pressure gauge 16, flow meters 17, filter cannister 18, and flexible tubing 19 and 21 leading to and from the face mask 22 applied to the patients face during ventilation. The customary valves within easy reach of the anesthetist afford control of gas pressures and volumes.

Connected to the ventilation system through a duct 23 is the customary flexible breathing bag 24, or reservoir, ordinarily of an elastomeric material. As stated above, the anesthetist has heretofore been required alternately to squeeze and release the bag, in cyclical fashion, whenever it was deemed necessary to assist the patients own efforts in inhaling and exhaling during the lung ventilation process.

To assist the anesthetist, cyclical compression and release of the reservoir 24 is effected herein by a pair of paddles 27 and 28. The paddles are formed with concave faces in opposed, facing relation, thereby conforming somewhat to the curved surfaces of the bag 24 when it is interposed between the paddles.

The paddles are moved, relatively, toward and away from each other; and preferably, one of the paddles, such as the paddle 27, is substantially fixed, although pivotable through a slight distance for signal control purposes, as will subsequently be described, and the other paddle, 28, is movable. The movable paddle 28 rocks to and fro between a substantially vertical attitude, in close juxtaposition to the substantially fixed paddle 27, and an inclined attitude approximately forty degrees from vertical, in which position all pressure on the interposed bag is released.

Rocking of the movable paddle 28 is effected by a crank mechanism, generally designated by the reference numeral 31, mounted on a frame 32 comprising a bottom plate 33, supported on a pedestal structure 34, and a vertical mounting wall 36 having a bottom flange 37 appropriately secured to the plate 33. Actuating the cranking mechanism in a conventional variable speed electrical motor 41 controlled as to speed by an exteriorly located knob 42. The knob 42, for accessability, is on top of a top closure plate 43, the plate 43 having depending pairs of side walls 44 and end walls 46 which, with the bottom plate 33 define a box-like housing 47 encompassing the actuating mechanism and electrical components. Around the base of the speed control knob 42 are indicia 48 such as the words Respiratory Increase with a corresponding arrow 49 indicating the direction in which the control is turned to effect an increase in the rate of respiration, i.e., the number of inhalation-exhalation cycles per minute.

The speed of the motor shaft is reduced by connection to a conventional gear box 51 from which protrudes a drive shaft 52 journaled in an opening in the mounting plate 36. Mounted on the end of the shaft 52 is a crank arm 53 driven by the drive shaft in the clockwise direction indicated by the arrow 56 in FIG. 2. Pivotally mounted on the distal end of the crank 53, as by a pin 57, is a lever 58, the remote end of which is pivotally connected by a pin 59 to the lower end of the rocker arm 61 of the movable paddle 28. The rocker arm 61, in turn, is pivotally mounted on a pivot pin 62 secured to the adjacent mounting wall 36.

The rocker arm 61 extends upwardly through an elongated opening 66 in the top closure plate 43, the edges of the opening being guarded by a rubber grommet 67. The upper portion of the rocker arm 61 affords means for detachable connection with the concavoconvex paddle 28, as by fastenings 70.

With the crank mechanism 32 in the position shown in FIG. 2, the movable paddle 28 is in a substantially vertical posture, parallel to the vertical substantially fixed paddle 27 and in close juxtaposition thereto in order to effect a substantially complete expulsion of the contents of the bag interposed therebetween as in FIG. 1.

When the crank arm 53 has revolved, in the clockwise direction 56, through 180 from the position shown in FIG. 2, the right hand portion of the lever 58 overlies the crank arm 53, and the pin 59 has moved toward the right a distance equal to twice the throw of the crank, thereby rocking the arm 61 about the fulcrum 62 and causing the arm 61 and the paddle 28 to incline toward the left and upwardly at an angle of approximately 40 from the vertical, the paddle in this position allowing the bag to expand to its maximum extent.

Continued rotation of the crank returns the movable paddle to upright position, the relative closure of the paddles again squeezing the interposed bag 24 (see FIG. 1) to substantially empty condition.

The cycle is continued until the ventilator is shut off by. rotation of the control knob 42 in a counterclockwise direction to OFF position. A pilot lamp 50 adjacent the knob 42 indicates whether the device is in OFF or ON condition.

Occasionally, a back pressure will build up in the ventilation system caused, for example, by an obstruction which has developed in the system or, more seriously, from a bronchial spasm or decreased compliance on the part of the patient. Where the anesthetist is effecting compression of the bag by hand, this back pressure is felt. Similarly, in the present machine, provision is made for sensing the back pressure and affording a warning, such as by a buzzer, which immediately alerts the anesthetist to a change in the system requiring attention.

The monitoring device, generally designated by the reference numeral 71, comprises a block 72 secured by fastenings 73 to the mounting wall 36. The block 72 extends upwardly through an elongated grommeted slot 74 in the top plate 43, the slot 74 also accommodating the vertical rod 76 to which the paddle 27 is detachably connected, by fasteners 70, the bottom end of the rod 76 being pivotally mounted by a suitable fastening 77 to the mounting plate 36.

Formed in the upper portion of the block is a through bore 81 oriented so as to intersect the vertical axis of the rod 76 of the paddle 27. An adjustment knob 82 carries a threaded stem 83 in threaded engagement with the adjacent tapped portion 84 of the through bore 81. The distal end of the threaded stem 83 engages the adjacent end of a helical spring 86 biasing in a left-hand direction (as appears in FIGS. 2 and 3) a plunger 87 abutting the vertical rod 76 carrying the paddle 27.

The plunger, in other words, biases the rod 76 in a counterclockwise direction, movement in such direction being opposed, however, by a limit stop pin 88 mounted on the wall 36.

The fastening 77 at the bottom end of the vertical rod 76 affords a pivoting movement to the rod, but since the limit stop 88 prevents further movement in a counterclockwise direction (see FIGS. 2 and 3) and the spring bias effected by the plunger 87 opposes move ment in a clockwise direction, the vertical attitude of the rod 76 can be deemed as substantially fixed in nature, at least with respect to movable paddle 28.

Nevertheless, the spring 86 will yield when a supervening force is applied against the plunger 87 in excess of the amount of the spring urgency. Such a force is exerted when an excessive amount of back pressure arises in the breathing bag during the compression (inhalation) portion of the respiration cycle. In this situation, the rod 76 is tilted slightly in a clockwise direction, about the pivot 77, owing to the force exerted by the movable paddle in swinging against the interposed breathing bag having excess back pressure, the bag, in turn, forcing the paddle 27 in a clockwise direction, as appears in FIGS. 1 and 2. In tilting slightly to the right (see FIG. 3), the rod 76 deflects the adjacent tip 91 of the spring leaf 92 of a microswitch 93 and depresses the customary button 94 into closed position, thereby sounding an alarm, such as a buzzer 96. By appropriate adjustment of the signal control knob 82, the anesthetist can set the mechanism to monitor back pressure and to provide the warning signal whenever the back pressure crosses a selected pressure threshold.

As appears most clearly in FIGS. 2 and 4, the power supply originates at a plug 101 and extends through conductors 102, 103 and 104, leading into a terminal box 106 to and from which extend various conductors, as will be described.

The conductor 102 is a common bus which extends through the switch 110 controlled by knob 42, and which not only affords ON-OFF capabilities but which also provides control of the motor speed (Respiratory Rate) by means of a conventional phase angle control circuit, generally designated by the reference numeral 108. The control circuit 108 includes, as shown in FIG. 4, identical diodes 109 and 111 (1N 4003) and a silicon controlled rectifier 112 (2N 4443). The SCR 112 is connected in series in the bus 102 and the gate terminal 113 of the SCR 112 is connected to a junction 114 of a conductor 116 attached to the diode 111 and a conductor 117 extending through a resistor 118 (47 ohms) and to the motor 41. A potentipreferred with respect to lowest, or threshold motor speed) are connected in the line 13, and a line resistor 132 (6.2K ohms) is also placed in the conductor 133 including the back pressure microswitch 93 and buzzer 96.

The conductor 133 and attendant elements are in shunt not only with the conductor 136 containing the pilot lamp 50, but also with the motor circuit. The AC ground 104 is grounded to the motor frame, as shown.

The capacitors 137 and 138 (both 0.05 mf.) between the bus 102 and ground 104, and between the conductor 103 and ground 104, respectively provide a filter effect which is most desirable in affording a nice degree of motor control.

In order to start the machine 12, the knob 42 is rotated a short distance in a clockwise direction to turn on the switch 110, further rotation in a clockwise direction being effective to increase the respiratory rate deemed most suitable by the anesthetist for the particular patient. The breathing bag 24 is thereupon inserted between the relatively reciprocating paddles so as to assist in ventilation. Should mechanical blockage, bronchial spasm or decreased compliance occur, the anesthetist is immediately alerted by an audible signal which is detected regardless of the attention being paid to the ventilating machine at the time. Prompt remedial action can thereupon be taken.

Removal of the bag, if necessary, and reinsertion thereof is readily accomplished, and the accessibility of all controls affords the user a conveniently operated ventilator machine.

In the usual case, the operation of the automatic ventilator is as follows. First, establish anesthesia with any of the standard anesthesia gas machines, such as the machine 13, using a 2 or 3 liter capacity reservoir bag with a gas flow rate of 2 to 6 liters per minute, as desired. Next, position the reservoir bag 24 between the paddles 27 and 28, as shown in FIG. 1, and adjust the appropriate respiratory rate valves as required for the particular patient. Also adjust the pressure relief valve 20 to allow proper filling of the patients lungs as well as the proper escape of excess gas. The pressure gauge 16 will, under these conditions, ordinarily attain a peak water pressure of about twenty centimeters, but will vary according to compliance, respiratory rate and other factors. The bag 24 must empty sufficiently to avoid pressure during the expiratory phase of the cycle. As previously indicated, the signal alarm 71 can be set to sound when pressures exceed the desired level. Tightening the thumb screw increases the pressure necessary to sound the alarm.

The paddles can be actuated by an electric motor, as

heretofore indicated, or by suitable mechanism, not shown, operated by compressed gas or liquid.

It can therefore be seen that I have provided an automatic ventilator for use in an operating room, in con- 5 junction with a conventional anesthesia gas machine,

which is versatile, safe, hygienic and easy to apply and use.

What is claimed is:

l. A ventilator for an anesthesia gas machine having a flexible gas reservoir bag connected thereto at one end and laterally exposed comprising:

a. a frame;

b. a pair of paddles;

c. means for cantilevering one of said paddles on said frame to project therefrom into lateral abutment with one exposed side of said bag;

d. means for movably cantilevering the other one of said paddles on said frame to project therefrom into lateral abutment with the other exposed side of said bag;

e. a rotary actuating means on said frame including an electric motor; and,

f. means including a crank and pitman for connecting said actuating means to drive said other paddle repeatedly to and fro and toward and away from said one paddle.

2. A ventilator as in claim 1 including a housing mounted on said frame, said one paddle projecting upwardly from said housing in a substantially vertical attitude, and said other paddle projecting upwardly from said housing and being movable between a first position approximately 40 to the vertical and a second position approximately vertical.

3. A ventilator according to claim 1 including a pivot mounting on said frame for said one of said paddles, a stop on said frame, and yielding means on said frame and engaging said one paddle for urging said one paddle toward said stop and toward said other one of said paddles.

4. A ventilator as in claim 3 further including warning means effective upon deflection of said one paddle resulting in compression of said yielding means.

5. A ventilator as in claim 4 wherein said warning means includes a signal member, and a pressure responsive switch connected tosaid signal member and closed by said deflection of said one of said paddles.

6. A ventilator as in claim 5 wherein said warning means includes adjustable means for controlling the ex tent of deflection of said one of said paddles required to actuate said signal member.

t t a 

1. A ventilator for an anesthesia gas machine having a flexible gas reservoir bag connected thereto at one end and laterally exposed comprising: a. a frame; b. a pair of paddles; c. means for cantilevering one of said paddles on said frame to project therefrom into lateral abutment with one exposed side of said bag; d. means for movably cantilevering the other one of said paddles on said frame to project therefrom into lateral abutment with the other exposed side of said bag; e. a rotary actuating means on said frame including an electric motor; and, f. means including a crank and pitman for connecting said actuating means to drive said other paddle repeatedly to and fro and toward and away from said one paddle.
 2. A ventilator as in claim 1 including a housing mounted on said frame, said one paddle projecting upwardly from said housing in a substantially vertical attitude, and said other paddle projecting upwardly from said housing and being movable between a first position approximately 40* to the vertical and a second position approximately vertical.
 3. A ventilator according to claim 1 including a pivot mounting on said frame for said one of said paddles, a stop on said frame, and yielding means on said frame and engaging said one paddle for urging said one paddle toward said stop and toward said other one of said paddles.
 4. A ventilator as in claim 3 further including warning means effective upon deflection of said one paddle resulting in compression of said yielding means.
 5. A ventilator as in claim 4 wherein said warning means includes a signal member, and a pressure responsive switch connected to said signal member and closed by said deflection of said one of said paddles.
 6. A ventilator as in claim 5 wherein said warning means includes adjustable means for controlling the extent of deflection of said one of said paddles required to actuate said signal member. 